1. Field of the Invention
This invention relates to a solid electrolytic capacitor, such as tantalum capacitor or aluminum capacitor, which comprises a capacitor element enclosed in a resin package. More particularly, the present invention relates to a solid electrolytic capacitor of the type wherein an anode and a cathode leads are bent outside a resin package toward the underside thereof for conveniently mounting to a surface of a printed circuit board.
2. Description of the Related Art
A solid electrolytic capacitor is known from Japanese Patent Application Laid-open No. 60(1985)-220922 for example. The capacitor disclosed in this Japanese document has such a structure as shown in FIGS. 6 and 7.
Specifically, the prior art capacitor comprises a capacitor element 1 which includes a capacitor chip 1a and an anode wire 1b projecting from the chip 1a. The capacitor also includes an anode lead 2 in electrical connection with the anode wire 1b, and a cathode lead 3 in electrical connection to the chip 1a. The capacitor element together with part of the respective leads 2, 3 is enclosed in a resin package 4, and the respective leads 2, 3 are bent toward the underside of the resin package 4 for conveniently mounting to a surface of a circuit board (not shown).
According to the prior art arrangement, the resin package 4 together with the projecting portions of the respective leads 2, 3 is symmetric with respect to a central plane transverse to the anode wire 1b. Therefore, the polarity of the capacitor is not visually recognizable, so that the capacitor may be erroneously mounted on a circuit board (not shown) in a reverse polarity. The capacitor thus erroneously mounted generates a lot of heat, consequently damaging the capacitor and it related components in a critical way.
As shown in FIG. 8, the polarity of the capacitor may be rendered visually recognizable by forming a slot 5 in the anode lead 2 and/or by forming a marking 6 on the upper surface of the resin package 4. However, the slot 5 is not readily recognizable due to its small size, whereas the marking 6 is not recognizable from below the capacitor.
Japanese Utility Model Application Laid-open No. 2(1990)-63525 discloses a solid electrolytic capacitor wherein a pair of anode wires (or both ends of a single anode wire) are made to project from two faces of a capacitor chip in electrical connection with a corresponding pair of anode leads while a single cathode lead is electrically connected to the chip. Thus, the two anode leads combined with the single cathode lead provide visual recognition as to the polarity of the capacitor.
However, due to the provision of the two anode wires projecting from the capacitor chip, the volume of the capacitor must be sufficiently enlarged to entirely enclose the anode wires, thereby resulting in a size increase. Further, since the respective leads are bent toward and concealed by the underside of the resin package, the visual recognition as to the polarity of the capacitor is inconvenient from above the capacitor. Moreover, since the anode leads project laterally from the resin package, though to a relatively small degree by bending toward the underside of the package, it is inevitable that the overall size of the capacitor inclusive of the package and the leads be correspondingly increased.